Recent results on D meson decays from BES
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Recent results on D meson decays from BES
陈江川 (for BES Collaboration)
Institute of High Energy Physics, Beijing China
高能物理学会第七届全国会员代表大会暨学术年会 广西 桂林
2006 年 10 月 27 日 -11 月 1 日
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Outline Introduction
Semileptonic decays of D mesons
Summary
Inclusive decays of D mesons
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The Beijing Electron Positron Collider (BEPC)
L ~ 11031 /cm2s at (3770) peak Ecm~2-5 GeV
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BESII Detector
VC: xy = 100 m TOF: T = 180 ps counter: r= 3 cm MDC: xy = 220 m BSC: E/E= 22 % z = 5.5 cm dE/dx= 8.5 % = 7.9 mr B field: 0.4 T p/p=1.7%(1+p2) z = 3.1 cm
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Muon identification can be done by the Muon Counter for the charged track with momentum of great than 0.55 GeV/c
dE/dx
TOF
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(3770) data sample
~18 pb-1 data taken at 3.773 GeV
~7 pb-1 data taken at the region from 3.768 GeV to 3.778 GeV
~8 pb-1 data taken in the energy region from 3.665 to 3.878 GeV
The total Luminosity is about 33 pb-1.
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Near DD-bar production threshold region
π–
With the singly tagged D sample, we can do some absolute measurements
e+
e-
D
D
K+
π–tag
D+
D-
X
π–
e-e+
D
D
K+
tag
0X
Singly tagged D sample
Absolute Measurements
0D
0D
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Semileptonic D Decays (1)Semileptonic D Decays (1)
e+
e-
Dtag
D+
D-
0K
π-K+
π-
e+
e-
Dtag
D0
K
π-0D
K+
D D
0
0
KD
,KD
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Motivation
Isospin conservation requires
2041)()/(00 ..eKDeKD ee
From PDG Br
1)()( 0 ll KlD/KlD
It is called “Longstanding puzzle” in Charm decay !
Is isospin conservation held in the D semileptonic dec
ays?
Recently:
070220081)(
)(0
0
...eKD
eKD
e
e
040050001)(
)(0
0
...eKD
eKD
e
e
BES-II published on Phys. Let. B608(2005)24-30
CLEO-c contributed paper at LP05 reports:
Solved the puzzle in Charm decays !
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CKM matrix elements &|| csV || cdV
Form factors & |)0(| f
Branching fractions
*
*
*
0Dc
u)(d
)( D
s ][d
u)(d
K ][
)( 0K][ || ||VV cdcs
)]0([ )0( ff K
Motivation
)()(00
KD/KD
5021)()(00 ..KD/KD
From PDG04 Br
|)0(| Kf
0
0
KD
, ,KD
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Charged track
photon
0 from , SK 22 yx < 0.08 m & |z| < 0.2 m
BSCE > 0.1 GeV 5firstHit22 ch
37 DC
85.0|cos|
Good track selection
Charged track with good helix fit
To be consistent with originating from the primary events vertex Vxy <0.02 m & |z| < 0.2 m
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Singly tagged modes KD0 , 0 K , K , 0
SK KD , 0K , KK 0 , KK ,
00 K, 0K
PID made by combining TOF, dE/dx & BSC information
CL > 0.1% ;
: K > CL K : CL
prob (2 , n ) > 0.1%, n = 1, 2, 3
Singly tagged D sample
1C kinematic fit
(mKnπ)
0 K,
, K ,
(Throughout the talk, charge conjugation is implied.)
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Invariant mass distribution for tags0D Invariant mass distribution for tagsD
34119875840 tagD
N 1601495321 tagD
N
,)(,)(
,)(,)(0000
00
KDdKDc
KDbKDa
S
KD0
00 KD
KD0
00
SKD
D)i(
KD)h( ,KD)g(
KD)f( ,KD)e(
,KKD)d( ,KKD)c(
,KD)b( ,KD)a(
SS
S
S
00
000
0
0
KD 0SKD
KKD S0
KKD
0SKD00 SKD
0 K K
D
9 modes
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Candidate modes KD0,
π:
CLKCL K :
;
0KD
μ :
missU selection
Double-tagged D decays (1)
80.
KCLCLeCL
CL
e
+
e-
D
D
tag
D+
D-
0K
π-K+
π-
Missing energy and momentum
missmissmiss PEU Should be around zero
missUmiss |U| 2
Nγ=0 (on recoil side of the D tag)
(or Nhit > 2 on μ counter)
Combined TOF , dE/dx & BSC information
80.
KCLCLeCL
CL
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νKD 0
data
Bckgrd DD-bar
MC
Data (subtracted bck)
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tags.)D of RECin (found 0
K ) tagsD of REC.in (found -0 K
Distribution of the Inv. masses of combinations
for the events for which the and
are observed in the recoil side
mKn
,K 0K
tags)D of REC.in (found 0
Preliminary
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Branching fraction
Experiment
BES
MARKIII
E687(93)
E687(95)
PDG 04
)( 0 KDBF
59.056.055.3
)( 0 DBF )(
0 KDBF
10.030.038.0
500490123 ...
170193 .. 030207 ...
8032310 ...
Results
[%] [%] [%]
130130243 ...
21030207 ....
An up limit at 90% C.Lis set to be <0.89%
Preliminary
hep-ex/0610019 & 0610020
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BES MARK III PDG04
)(
)(0
0
KD
KD15.024.087.0 5021 .. 5021 ..
Ratio of partial width
Obtained based on the branching fractions quoted from PDG04
Preliminary
The ratio of Br. for D0 decays to K(π)μν is:
03.009.011.0)(
)(0
0
KDBr
DBr
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Semileptonic D Decays (2)Semileptonic D Decays (2)
e+
e-
Dtag
D+
D-
0*Ke
e
π-K+
π-
e+
e-
Dtag
D0
*Ke
e
π-0D
K+
D D
e*
e
e*
e
eK ,eKD
eK ,eKD
0
00
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Candidate modes
π: CLKCL K :
e :
missU selection
Combined TOF and dE/dx information
80
0010
.KCLCLeCL
eCL
and .eCL
e+
e-
D
D
tag
D+
D-
0*Ke
π-K+
π-
Missing energy and momentum
missmissmiss PEU Should be around zero
missUmiss |U| 3
0010.CL
e*
e
e*
e
eK ,eKD
eK ,eKD
0
00
Double-tagged D decays (2)
Combined TOF , dE/dx & BSC information
2200 c/MeV |MM|SK
KS0:
νe
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eeKD
eeKD 00
eeKD 0*
eeKD *0
Events found in REC. of Dtag
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Results:Published in Eur. Phys. J. C47 (2006) 31
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Results:
With the measured branching fractions in this work and
quoted from BES-II earlier work, we obtain:
%...eKDBF
%...eKDBF
e
e
270400823)(
670591958)(0
0
Published in Eur. Phys. J. C47 (2006) 31
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Comparison
)(
)(
l
l*
lKD
lKD
uncertainty of theoretical
prediction
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Inclusive Decay Branching Fractionsfor
XK/K ,XK/KD 0** 0
e+
e-
Dtag
D+
D-
0*K
π-K+
π-
e+
e-
Dtag
D0
*K
π-0D
K+
D D
X X=any particles
K–
π+π –
0K
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Motivation
Serving as a check on the sum of the branching fractions for the exclusive D decay.
Providing information about the relative strength of Cabibbo-favored and Cabibbo suppressed D decays.
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Candidate modes
π: 0.001KCL& CLKCL K :
Combined TOF and dE/dx information
0010.CL
XK/KD ,XK/KD
XK/KXK/K ,XK/KXK/KD
XK/KXK/K ,XK/KXK/KD****
****
00000
0000
00000
Double-tagged D decays
cmLxycm. &|MM|SKS
MK8703
00 KS0:
e+
e-
Dtag
D+
D-
0*K
π-K+
π-
D
X=any particles
K–
π+
e+ D0
*K
0D
D
Xπ –
e-
0K
The Kπ with maximum CL(K)•CL(π) retained in an event
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D0 signal region
D0 sideband
K +π –
K –π+K+π –
XKXKD * 0XKXKD * 0
XKXKD * 00
Cabibbo favored decay Cabibbo suppressed decay
XKXKD * 00
K –π+ K+π –
D – signal region
D – sideband
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Results
%...XKDBF * 210478)( 00
Cabibbo favored decay:
%...XKDBF * )035423(2)( 0
Cabibbo suppressed decay:
%...XKDBF * 402182)( 00
C.L. 90%at 66)( 0 %.XKDBF *
%..XK
XKsum*
*
02123)BF(D
% 0.88.1)BF(D :PDG04 BF exclusive of 0
00
Published in PLB625 (2005) 196
)20(1.5)(or 921.0-
0 %.XKDBF .*
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Neutral K decay of D: Charged K* Decay of D: XK/KD **
e+
e-
Dtag
D0
*K
0D
K+
D
X
0K
π –
π+π –
KS0
Removing double counting with sideband background.
XK/KD 00
3σ
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D0 signal region
D0 sideband
XK/KD 000
XK/KD 00
D+ signal region
D+ sideband
π+π –
π+π –
Preliminary
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X K D
*
0 X K D*
D0 signal region
D0 sideband
X K D*
0
X K D*
K S
0π –K
S0π –
K S
0π + K S
0π +
Preliminary
Mass(GeV/c2)
Mass(GeV/c2)
Mass(GeV/c2)
Mass(GeV/c2)
D – signal region
D – sideband
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Results
% 0.38.46.47)/( 000 XKKDBF
% 3.35.55.60)/( 00 XKKDBF
% 9.13.83.15)( *0 XKDBF
% )7.02.57.5()( * XKDBF
%6.3)( *0 XKDBF
% 3.20)( * XKDBF
Cabibbo favored decay:
Cabibbo suppressed decay (at 90% C.L.):
The results submitted to PLB
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Comparison
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BES measured semileptonic D decay branching fractions
.
.
% 8.03.23.10)(
% 10.030.038.0)(
% 59.056.055.3)(
0
0
0
KDBF
DBF
KDBF
03.009.011.0)(
)(0
0
KDBr
DBr
The ratio of branching fractions is
Summary
Ratio of partial width BES MARK III PDG04
)(
)(0
0
KD
KD15.024.087.0 5021 .. 5021 ..
.
Preliminary
hep-ex/0610019 & 0610020
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Summary
.
Measured semileptonic D decay branching fractions
% )27.075.050.3()( eeKDBF
% 28.004.161.2)( 00 eeKDBF
% 40.021.106.5)( 0* eeKDBF
% 39.048.187.2)( *0 eeKDBF
With the measured branching fractions in this work and quoted from BES-II earlier work, we obtain:
%...eKDBF%...eKDBF ee 270400823)( , 670591958)( 00 .
02.017.057.0)(
)(0
0*
e
e
eKD
eKD
Published in Eur. Phys. J. C47 (2006) 31
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Summary
.
Measured branching fractions for inclusive Cabibbo favored and suppressed decays of D mesons:
%...XKDBF * )210478()( 00 Cabibbo favored decay:
%...XKDBF * )0354223()( 0
Cabibbo suppressed decay:
%...XKDBF * )402182()( 00
C.L. 90%at 66)( 0 %.XKDBF *
)%..()XKBF(D
0.8)%(8.1)XKBF(D :(PDG04) BF exclusive of sum*
*0
021230
0
Published in PLB 625(2005)196
)20(1.5)(or 921.0-
0 %.XKDBF .*
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SummaryCabibbo favored decay:
Cabibbo suppressed decay (at 90% C.L.):
%)0.38.46.47()/( 000 XKKDBF
%XKKDBF )3.35.55.60()/( 00
Branching fractions of inclusive neutral K decay of D .
.
.
% )9.13.83.15()( *0 XKDBF
)%7.02.57.5()( * XKDBF
%6.3)( *0 XKDBF
%3.20)( * XKDBF
The results submitted to PLB
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谢 谢!
Thank You !